Multilobe omnirange beacon systems



L. HlMMr-:L 2,713,163

MULTILOBE OMNI'RANGE BEACON SYSTEMS 2 Sheets-Sheet l Ow- Om o o5 en July12, 1955 Filed Dec. 14, 1951 INVENTOR LEN HMMEL BY /wy l ATTORNEY l..HIMMEL MULTILOBE. OMNIRANGE BEACON SYSTEMS July 12, 1955 2 Sheets-Sheet2 Filed Dec. 14, 1951 INVENTOR LEO/Y H/MME L ATTORNEY 2,7l3,l63 PatentedJuly 12, 1955 MULriLonn oMNntANcE nnacoN SYSTEMS Leon Himmel, CedarGreve, N. J., assigner to International Telephone and TeiegraphCei-poration, a corporation of Maryland Application December 14, 1951,Serial No. ZLSS 13 Claims. (Cl. 343-106) This invention relates tomultilobe omnirange beacon systems and more particularly to means forrotating a multilobe radiation pattern goniometrically.

In omnirange beacon systems heretofore employed operating in the 100 mc.region and radiating essentially a rotating cardioid and a carrier onwhich is modulated a reference signal, considerable diiculty has beenexperienced with errors due to reflections of the radiated signal. It iswell known that the use of harmonies in the radiation pattern willincrease the sharpness of the null point of the radiation pattern andthus aid in minimizing these reflection errors. The radiation ofharmonic patterns in -omnirange beacons has in the past beenaccomplished only by utilizing unwieldy rotating antenna arrays manywavelengths in diameter or by complicated switching means usingstationary arrays wherein the rotation is effected in steps.

One of the objects of this invention, therefore, is to provide anomnirange beacon system for effecting ro- -tation of a harmonicradiation pattern without the use of rotating antennas or complicatedswitching means.

Another object is to provide goniometric rotation of a harmonicradiation pattern.

A further object is to provide an antenna system which rotates a strongharmonic radiation pattern with out serious distortion and which is freefrom Vradio irequency phase shift as a function of azimuth angle.

Brieiiy, by this invention an R. F. energy source is coupled to themotor-driven rotor of a goniometer. A circular antenna array having aplurality of antennas alternately phased and 180 is connected to one eldwinding of the goniometer. The second ield winding of the goniometer, inquadrature relation to the rst iield winding, has coupled to it a secondcircular antenna array comprising a plurality of antennas alsoalternately phased 0 and 180, the antennas thereof be- I inginterspersed with the antennas of the first array. An antenna situatedin the center of the two arrays is coupled to the R. F. energy sourceand provides a nondirective R. F. carrier signal for the harmonic sideband radiations. To provide for proper co-phasal relation between thecarrier and harmonic signals, a variable phase adjuster is introducedbetween the goniometer and the source of R. F. energy. An amplitudeadjuster divides the power output of the transmitter between the carrierantenna and the circular antenna arrays and thus provides the propermodulation relation between the carrier and harmonic signals.

AOne of the important features of this invention is the method ofproducing a desired multilobe radiation. In accordance with theprinciples of this invention, the goniometer output is sequentially fedto the harmonic array described above and toa concentric antenna arrayradiating a rotating cardioid pattern. Means are provided todistinctively modulate each radiation pattern. The central antennaprovides a nondirective R. F. carrier signal modulated with a bearingreference signal.

The receiver contains lmeans to demodulate the received signals and `tocouple the demodulated signals to Suitable phase comparison circuitswhere the phase difference of the bearing reference signals and the nullpoint of the side band signals is determined. Means are provided foridentifying the side `band radiation pattern being transmitted. Themultilobe harmonic side band signal is prevented from reaching theindicating means until the indication derived from the fundamental orcardioid side band radiation is within a predetermined indication rangethus preventing ambiguities from arising due to the plurality of nullpoints of the harmonic signal. Since the radiation pattern of themultilobe harmonic array will have greater sharpness, the null point maybe determined with greater accuracy thus making possible a more accuratemeasurement of the phase difference of the bearing reference signal andthe null point of the side band radiation.

The above-mentioned and other features and objects of this invention andthe manner of attaining them will become more apparent by reference tothe following description taken in conjunction with the accompanyingdrawings, wherein:

Fig. l illustrates in block schematic form an embodiment of thisinvention for the rotation of a harmonic pattern;

Fig. 2 illustrates an omnirange beacon system `in accordance with theprinciples of this invention; and

Fig. 3 illustrates the radiation pattern o'f the omnirange beacon ofthis invention.

Referring to Fig. l, an antenna system for rotatingA a multiloberadiation pattern goniometrica'lly is shown comprising a signal source1, a Atransmitter 2, an amplitude adjuster 3, a `phaser 4, a goniometer5, Va center carrier antenna 6, and a circular antenna array 7 composedof two series of antennas 7a and 7b. The R. F. energy is coupleddirectly to the amplitude adjuster 3 which divides the R. F. energybetween the center antenna 6 and the circular antenna array '7, thusadjusting the relative amplitude or per cent modulation of the radiationfrom the two antenna arrays 6 and 7. The center antenna 6 radiates anondirectional R. F. carrier signal. The portion of the output 'ofamplitude adjuster 3 coupled to the circular antenna arr-ay 7 :is firstfed to phaser 4 vwhich adjusts the -phase relation between the side bandsignal of the circular antenna array 7 and the R. F. carrier signal ofthe center .antenna 6. The correctly phased and amplitude adjusted R. F.energy from the transmitter 2 is 'then fed to the motor-driven rotor oflgoniometer 5. One Lfield Winding of the goniometer 5 is coupled toantenna series 7a and the other field winding to antenna yseries 7b.VPhase Shifters 9 are provided to produce a 180 phase shift betweenalternate antennas of each series coupled to each iield winding. It isto be clearly understood that the use of phase Shifters 9 is forpurposes Yof illustration only and any means known Yto those skilled inthe art may be employed to produce a phase shift between alternateantennas of each series.

To rotate a multilobe radiation pattern, the 'transmitter 2 suppliespart of the R. F. energy to the carrier antenna 6 through the amplitudeadjuster 3. This produces a nondirective carrier frequency pattern. Theeld windings of goniometer 5 supply side `band .currents to the antennasof the circular varray 7. This produces a rotating field which rotatesat the modula* tion frequency of the goniometer 5. vSince alternateantennas of the circular array 7 are fed from the same field winding andthe iield windings .of goniometer 5 are in quadrature relation, oneseries of antennas .7a will lead the other series of antennas 7b by 90.

The R. F. energy in the central antenna 6 is adjusted,

by means of phaser 4, to be in phase with the side band currents in thecircular antenna array 7. The fields established by the energy fed tothe circular array 7 are such that the net effect of the modulatedfields is to establish a multilobe field which rotates about the centerof the circular array 7 at the frequency of rotation of the goniometerrotor. When the center antenna 6 is energized by the R. F. energy fromthe transmitter 2, an R. F. field is established having a normallycircular pattern which will combine with the multilobe pattern of thecircular array 7, with which it is in phase, to establish a field havinga multilobe pattern rotating about the central antenna 6 at a rotationfrequency equal to the rotation of the goniometer rotor. Due to phaseShifters 9 alternate antennas of each series are of opposite phase, thusone lobe of a multilobe radiation pattern will be radiated for everyfour antennas in the circular array 7. An amplitude adjuster 3 isprovided for adjustment of the per cent modulation of the carrier by theside band currents. Any known amplitude adjuster may be used, onesuitable type of amplitude adjuster that may be used being disclosed inmy copending application, Serial No. 241,122, filed August 9, 1951,entitled Amplitude Control Unit.

Referring to Fig. 2, a multilobe omnirange beacon system in accordancewith the principles of this invention is shown comprising a signalsource 1 and a transmitter 2 coupled'to an amplitude adjuster 3. Part ofthe R. F. energy from the amplitude adjuster 3 is fed to a centercarrier antenna 6. The radiation from the carrier antenna 6 isnondirectional and of constant phase through-` out the 360 of azimuth.The carrier signal coupled to antenna 6 is first modulated by anywell-known means to provide a bearing reference signal. The remaining R.F. energy from amplitude adjuster 3 is fed through phase adjuster 4 tothe rotor of goniometer 5. The rotor of goniometer 5 is driven by motor11 which is synchronously coupled to bearing reference modulator 10.Switch 12 alternately couples the output of the goniometer 5 field coilsto the circular antenna array 7 and to the cardioid antenna array 13.Modulator 14, responsive to switch 12, varies the frequency of thesubcarrier signal. Assume for purposes of this explanation that when theoutput of goniometer 5 field coils is coupled to the cardioid antennaarray 13, the bearing reference signal modulates a 10 kc. subcarrier,and when the output of the goniometer 5 field coils is coupled to thecircular antenna array 7, the bearing reference signal modulates an 8kc. subcarrier thus providing means for the receiver to identify whichantenna array is radiating side band signals. As the rotor of thegoniometer 5 revolves, assume motor 11 drives the rotor at 30 c. p. s.,the voltage fed to the cardioid array 13 varies sinusoidally at the rateof goniometer rotation and modulates the R. F. energy of the carrierantenna 6 to produce a rotating cardioid pattern as indicated in Fig. 3,curve A. The voltage fed to the circular antenna array from the fieldwindings of goniometer 5 produces a rotating multilobe side bandmodulation of the R. F. carrier energy from antenna 6 as hereinbeforeexplained and as indicated in Fig. 3, curve B. The phaser 4 is adjustedto maintain the proper phasal relations between the R. F. carrier fieldand the rotating fields of antenna arrays 7 and 13. The amplitudeadjuster 3 changes the per cent modulation of the carrier energy by theside band radiations. Thus the transmitted signal comprises an R. F.carrier signal, frequency modulated with a bearing reference signalalternately on an 8 kc. or 10 kc. subcarrier, respectively andalternately amplitude modulated by the side band radiations due to thecircular antenna array 7 and antenna array 13 as indicated in Fig. 3.

The phase difference between the bearing reference signal and the nullpoint of the cardioid radiation depends on the azimuth of thetransmitter from the receiver.

Hence by measuring this phase difference the bearing to the transmitterfrom the receiver may be determined.

The receiver section of this multilobe omnirange system, Fig. 2,comprises a receiver 15 to receive the transmitted signals. The bearingreference signal is filtered from the carrier by means of a 10 kc.filter 16 and an FM detector 17 or an 8 kc. filter 18 and FM detector19. The detected bearing reference signal is coupled directly to thephase comparators 20 and 21. The cardioid and multilobe side bandsignals are passed by a filter 22 tuned to the frequency of thegoniometer 5 rotation, 30 cycles per second. The filtered side bandsignals are coupled to switch 23. Switch 23, responsive to FM detectors17 and 19, couples the output of the 30 cycle filter 22 due to thecardioid radiation from antenna array 13 to phase comparator 20 which iscoupled to indicator 24 in a 1:1 ratio. Thus, a one degree phasedifference between the bearing reference signal and the null point ofthe cardioid radiation as determined by phase comparator 20 will changethe reading of indicator 24 one degree. The comparison of the cardioidradiation and the bearing reference signal is necessary to preventambiguities from arising from the comparison of the bearing referencesignal and a null point of the multilobe radiation. The multiloberadiation will have a null point for each lobe or for each four antennasin the circular array 7. When the indicator 24 is within an indicatingrange which prevents ambiguities from arising, due to the plurality ofnull points of the multilobe radiation, as indicated by dotted lines cand c' of Fig. 3, the holding relay 25 activates switch 23 which thencouples the output of the 30 cycle filter 22 to phase comparator 21which is geared to indicator 24 in an Nzl ratio, N being the number oflobes radiated by the circular antenna array 7 which is proportional tothe number of antennas in the array 7. Since the slope of the harmonicradiation as illustrated in Fig. 3 is sharper than that of the cardioid,the error of the indicator 24 can be reduced accordingly. In addition,it is well known that the error of the indication due to reflection ofthe transmitted signal will be reduced proportional to the order ofharmonic radiated.

While I have described above the principles of my invention inconnection with specific apparatus, it is to-be clearly understood thatthis description is made by way of example only and not as a limitationto the scope of my invention as set forth in the objects thereof and inthe accompanying claims. l

I claim:

l. An antenna system for radiating a multilobe radiation patterncomprising a source of R. F. energy, a first series of at least fourantennas arranged in a circle, a second series of at least four antennasinterspersed with the antennas of said first series, means to couple theR. F. energy to said first series, means to couple the R. F. energy tothe said second series of antennas in quadrature relation to the R. F.energy coupled to said first series of antennas, and means reversing thephase of the R. F. energy fed to alternate antennas of each of saidseries.

2. A radio beacon system for rotating a multilobe radiation patterncomprising a source of R. F. energy, a first series of at leastfourantennas arranged in a circle, a second series of at least four antennasinterspersed with the antennas of said first series, means to couple theR. F. energy to said first series of antennas in phase sequence, meansto couple the R. F. energy to the said second series of antennas inphase sequence in quadrature lrelation to the R. F. energy coupled tosaid rst series of antennas, and means reversing the phase of the R. F.energy coupled to alternate antennas of each of said series.

3. A radio beacon system for rotating a multilobe radiation patterncomprising a source of R. F. energy, a goniometer having two field coilsin quadrature relation and a rotor coil, means to rotate said goniometerrotor coil, means to couple said R. F. energy to said rotor coil, afirst series of at least four antennas arranged in a circle,

a second series of at ieast four antennas interspersed with the antennasof said rst series, means to couple one said goniometer field coils toantennas of said first series, means to couple the second of saidgoniometer iield coils to said second series of antennas, and meansreversing the phase relation of alternate antennas of each of saidseries.

4. A beacon system for rotating a multilobe radiation pattern comprisinga source of R. F. energy, a nondirectional antenna, means to couple saidR. F. energy to said nondirectional antenna, a goniometer having two eldcoils in quadrature relation and a rotor coil, means to rotate Saidgoniometer rotor coil, means to couple said R. F. energy to said rotorcoil, a iirst series of at least four antennas arranged in a circleabout said nondirectional antenna, a second series o at least fourantennas interspersed with the antennas of said iirst series, means tocouple one of said goniometer iield coils to said first series ofantennas, means to couple the second of said iield coils to said secondseries of antennas, and means reversing the phase of alternate antennasof each of said series.

5. A 'Deacon system according to claim 4, wherein said means to couplethe R. F. energy to the said goniometer' rotor coil further includesmeans to vary the phase of the said R. F. energy coupled to said rotorcoil.

6. A beacon system according to claim 4, wherein said means to couplethe R. F. energy to the said goniometer rotor coil and said means tocouple the R. F. energy to said nondirectional antenna further includesmeans to adjust the relative amplitude of said R. F. energy coupled tosaid goniometer rotor and to said nondirectional antenna.

7. In an omnirange beacon having a source of R. F. energy coupled to acarrier antenna and to a goniometer, and antenna means coupled to eldcoils of said goniometer, to radiate a rotating cardioid pattern; a rstseries of at least four antennas arranged in a circle, a second seriesof at least four antennas interspersed with the antennas of said iirstseries, means to couple said iirst series to one of said goniometeriield coils, means to couple said second series to second of saidgoniometer field coils, means reversing the phase of alternate antennasof each series, and means to alternately feed the goniometer output tosaid antenna means to radiate a cardioid pattern and to said first andsecond series of antennas to radiate a multilobe pattern.

8. An omnirange beacon according to claim 7, wherein said means tocouple the source of R. F. energy to said carrier antenna furtherincludes means to modulate the R. F. energy according to which antennassaid output is coupled.

9. A multilobe omnirange beacon system comprising a source of R. F.energy, means to modulate said R. F. energy with a bearing referencesignal, a nondirective` antenna, means to couple said nondirectiveantenna to said source of modulated R. F. energy, a goniometer having arotor and two field coils in quadrature relation, means to rotate saidrotor, antenna means associated with said nondirective antenna coupledto said iield coils of the goniometer to produce a rotating cardioidradiation pattern, a first series of antennas arranged in a circle aboutsaid associate antenna means, means to couple said series of antennas toone of said goniometer eld coils, a second series of antennasinterspersed between antennas of the said iirst series, means to couplesaid second series of antennas to the said second field coil of saidgoniometer, means reversing the phase of alternate antennas of eachseries, means to alternately interrupt the coupling of said associateantenna means and said series of antennas to said goniometer eld coils,means to modulate the energy radiated from said nondirective antenna andaccording to which antennas said output is coupled, a receiver toreceive the transmitted signals, means to demodulate the bearingreference signal, means to lter out the signals due to the associateantenna means, means to lter out the signals due to said iirst andsecond series of antennas, a plurality of phase comparator means, meansto couple the said bearing reference signal to said phase comparatormeans, means to couple the signal due to the associate antenna means toone of said phase comparators, indicator means to indicate results ofsaid phase comparison operation, means responsive to said 'ndicator tocouple the signal due to said irst and second series of antennas to thesecond phase comparator, and means to indicate results of said secondphase comparison operation.

l0. A multilobe omnirange beacon transmitting system comprising a sourceof R. F. energy, means to modulate said R. F. energy with a bearingreference signal, a nondirective antenna, means to couple saidnondirective antenna to said source of modulated R. F. energy, agoniometer having a rotor and two ield windings in quadrature relation,means to couple said goniometer rotor to said source o' R. F. energy,means to rotate said rotor, antenna means associated with saidnondirective antenna, means to couple said antenna means to said eldcoils of said goniometer to produce a rotating cardioid pattern, aplurality of antennas alternately of opposite phase in a rst circulararray about said cardioid array, means to couple said circular antennaarray to one o said goniometer iield coils, a second circular antennaarray having a plurality of antennas alternately of opposite phaseinterspersed between antennas of said rst circular antenna array, meansto couple said second circular array to a second field coil of saidgoniometer, switching means to sequentially interrupt the coupling ofsaid antenna means and said circular antenna arrays to said field coilsof the goniometer, and modulator means to modulate said radiated energyin accordance with the position of said switching means.

1l. A multilobe omnirange beacon transmitting system according to claiml0, wherein said means to couple said source of R. F. energy to saidgoniometer rotor and to said nondirective antenna further includes meansto adjust the relative amplitude of the said R. F. energy coupled tosaid rotor coil and to said nondirective antenna.

12. A multilobe omnirange beacon transmitting system according to claim10, wherein said means to couple said goniometer rotor to said source ofR. F. energy further includes means to vary the phase of said R. F.energy coupled to said goniometer rotor.

13. A receiver to receive an omnirange radio signal which includes au R.F. carrier modulated with a bearing reference signal and alternately arotating cardioid radiation pattern and a rotating multiiobe radiationpattern, comprising a receiver to receive the transmitted signals, meansto demodulate the bearing reference signal, means to lter out thebearing reference signals, means to lter out the cardioid and multilobesignals, a plurality of phase comparator means, means to couple the saidbearing reference signal to said phase comparator means, means to couplethe bearing reference signals to one of said phase comparators,indicator means to indicate results of said phase comparison operation,means responsive to said indicator to couple the cardioid and multilobesignals to the second phase comparator, and means to indicate results ofsaid second phase comparison operation.

References Cited in the le of this patent UNITED STATES PATENTS1,379,541 Murray May 24, 1921 2,252,699 Byrne Aug. 19, 1941 2,422,110Luck inne 10, 1947 2,511,030 Woodward .lune 13, 1950

